Is safe, green thorium power finally ready for prime time?

If you’ve not been tracking the thorium hype, you might be interested to learn that the benefits liquid fluoride thorium reactors (LFTRs) have over light water uranium reactors (LWRs) are compelling. Alvin Weinberg, who invented both, favored the LFTR for civilian power since its failures (when they happened) were considerably less dramatic — a catastrophic depressurization of radioactive steam, like occurred at Chernobyl in 1986, simply wouldn’t be possible. Since the technical hurdles to building LFTRs and handling their byproducts are in theory no more challenging, one might ask — where are they?

The enrichment of natural uranium is the first and perhaps most difficult step to building nuclear weapons. LWRs, which by their nature require enriched uranium, were the logical choice at the dawn of the nuclear age to develop an industry around. Richard Martin, a writer for Wired and author of Superfuel: Thorium, the Green Energy Source for the Future, summarized the argument a little more succinctly: the US abandoned thorium reactors because they didn’t produce plutonium bombs. The larger truth, of course, is a little more complex.

Today’s nuclear industry might be described as an elephant. It would be very difficult for an elephant to evolve wings (thorium) because big animals just do not evolve wings — little animals evolve wings and they in turn might evolve into bigger animals with wings. The chosen gimmick of the proto-elephant was the trunk (uranium), at first just a little one, but as elephants got larger, their trunks got really really large; it became their defining feature.

The molten salt reactor (MSR), predecessor of the LFTR, lost out to the LWR in the early ’50s for a simple reason. When Navy Admiral Hyman Rickover got wind of the possibilities of nuclear power, he wanted and got nuclear-powered submarines. Unfortunately for the MSR, sodium would react violently if it accidentally contacted water. The baby nuclear elephant would be a small machine, but light water uranium reactors, which already had a little head start, would be the technology. It also didn’t help the case for MSRs that naval and shipyard engineers were already the best in the world at working with water. They were experts at building the corrosion resistant pumps, valves, bearings and other machinery needed to utilize it. But as Martin keenly observes in Superfuel, five decades later we see that the essential element of today’s technology, pressurized water, has become its Achilles heal.

Weinberg continued to pour his efforts into a small, workable MSR to be used as a powerplant for a nuclear airplane. This was an unfortunate misdirection. In a time when there were actual plans to use nuclear technology to dam the Straight of Gibraltar and reclaim lands long ago submerged under the Mediterranean, the idea of a nuclear airplane was not so absurd. The Cold War not withstanding, in times of prevailing peace, a flying nuclear reactor cannot count its first success as managing not to crash and destroy itself. The US and Russia ran similar programs and flew test reactors on board conventional aircraft, but ultimately both projects were scrapped.

Many people think it is not too late today, to attempt put some muscle into Dumbo’s ears so to speak, and revisit the thorium reactor. Several private efforts in the US have sprung up, led by entrepreneurs who have the knowledge necessary to do so. One project undertaken by Terrapower, funded through Microsoft’s Intellectual Ventures, is trying to build a device called a travelling wave reactor. It is a little more exotic than the MSR technology from decades ago and will require considerable effort to realize. Other homegrown efforts by start-ups like Flibe Energy, Thorium Power, and Lightbridge are struggling to fund their projects without visible government support.

Flibe Energy is looking to make ends meet by exploiting the fact that LFTRs are very good at producing medical isotopes like molybdenum-99, 90% of which we currently import from Canada. Our looming medical isotope problem is irresponsible and inexcusable as these isotopes are critical to patient diagnoses and treatment. Any health care system which fails to provide for their reliable procurement will only accelerate current medical cost inflation. Transatomic is another US-based company scrapping to survive. It is now running tests using the IR-8 research reactor at the Kurchatov Institute in Moscow. Thorium Power, based outside of Washington DC, is also working with Russian scientists to use thorium fuel — not to directly generate energy, but instead to burn surplus military plutonium.

Tagged In

Though the author makes a compelling point for the LFTR technology…lets clarify a few things:
A. LFTR LWR, MSR(LSR) and HWR, refer to the reactor plants primary coolant; that highly pressurized material that interfaces with the steam generator (boiler) that turns the water into steam that turne the turbines to make electricity.
B. The accident at Chernobyl had nothing to do with LWR technology, the Soviets have long preferred MSR, specifically Liquid Sodium, as thier primary cooling medium due to its extremely high efficiency in reatining heat, compared to LWR and HWR, at the expense of safety.
C. Our use of LWR and HWR is due in part to safety.. if there is a leak, steam forms, and a steam cloud only travels so far before it dissipates in the case of accidental exposure, whereas sodium
a) explodes
b) causes fires
c) has the potential to carry radiation hundreds of miles once it vaporizes.
(sound familiar)
Additionally, water reactors allow for far more redundant safeguards, why do you think the US Navy has not had any major recordable incidients in over 50 years of operating these plants.

A. LWR and HWR generally refer to light water reactor and heavy water reactor respectively, both of which tend to be pressurized water reactors. One of the key advantages of MSRs in general and the LFTR in particular is that those reactors are not pressurized and the coolant is a solid at room temperature.

C. While LWR and HWR technology is certainly safer than liquid sodium technology, MSR technology is even safer for a number of reasons including operating at atmospheric pressure, coolant that is solid at room temperature, and a failsafe design in case of total power failure consisting of a freeze plug at the bottom of the vessel that has to be actively cooled.

The RBMK is a light-water-cooled, graphite-moderated reactor (LWGR), which is not a variant of LWR.

W. Scott Meeks

Ah, you are correct; I was sloppy with my wording. I should have said “variant of a water-cooled reactor”. Thanks.

Uzza

Just to clarify, the active cooling needed for the freeze plug is to keep it frozen, as otherwise the fuel would drain in to a storage tank and shut off the reactor.

http://peakvt.blogspot.com PeakVT

“the Soviets have long preferred MSR, specifically Liquid Sodium, as
thier primary cooling medium due to its extremely high efficiency in
reatining heat,”

Not true. The Soviets only built a few sodium-cooled LMFRs. The primary power reactor type is the VVER, which is their acronym for Soviet-designed PWRs. The second most common type is the RBMK. The Soviets also built several lead-bismuth eutectic-cooled LMFRs for their submarines, which were basically failures. But the majority of submarines were powered by PWRs.

http://www.facebook.com/people/Damon-Hill/100000905925297 Damon Hill

Isn’t it the French who have a number of liquid metal sodium reactors?

energy_guy

Nope, why not just google for “liquid metal sodium reactors” and find out.

WhatTheFlux

Yes, let’s clarify a few things:

Liquid sodium has nothing — at all — to do with molten salt.

An MSR is a liquid fuel molten salt reactor. It operates at atmospheric pressure. The soviets favored an LMBR – a solid fuel, liquid metal breeder reactor, typically molten lead or molten sodium. These are two totally different reactor designs than a molten salt reactor.

Liquid sodium is a molten metal, and molten salt is, well, a molten salt. Salt is one of the most stable substances in the universe, and molten salt operates at ambient atmospheric pressure. It is not “highly pressurized” at all. Period. While it is indeed hot enough to flash water into steam to spin a turbine, that would be a waste of heat. It’s much more efficient to use an inert gas.

If a molten salt reactor leaked, the molten salt would flash any water in the immediate vicinity into steam as it cooled. Visualize molten lava cooling on a beach. But that’s it. It would not – NOT – start a fire, as molten Sodium would. Again, they are two totally different substances, and two totally different reactor designs.

And since molten salt does not operate under pressure, it does not have volatile fission products in the reactor that, if they leak, would send “radiation hundreds of miles once it vaporizes.” This is not, in any way, shape, or form, how a molten salt reactor would work, or how it would act if it leaked or is destroyed. At all. Period.

You are conflating the workings of a pressurized, water-cooled, solid fuel reactor and a solid-fuel, liquid-sodium-cooled fast reactor, with a no-pressure, no-water-cooling, liquid fuel reactor. They are two completely, totally, utterly different reactor designs, two completely different schools of thought, chemistry, and engineering.

And the Navy hasn’t had a major recordable accident because they are highly trained professionals with excellent equipment. Operated properly and away from quakes and tsunamis, solid fuel reactors are fine. Molten salt reactors are just safer, cheaper, more efficient, much more foolproof, and much more parsimonious as to fuel consumption and waste production.

greybirdtoo

Bravo on the Navy clarification, but another factor to go with the training and equipment, is the robust and safety redundant design of US Naval reactors. The designs were focused on reliability and safety from the beginning. The training of the operating crews is top notch and continuous and designed to compliment the safety and reliability of the designs. (As you might guess, I’m a little familiar with the topic.)

Jim Fox

Have you forgotten the Thresher disaster?
I worked on the UK team that reviewed the operating manuals
supplied to MOD(N), UK. We found a great many design flaws,
mainly in the area of incompatible materials- one of which led directly to the loss.

greybirdtoo

I am aware of the Thresher, the lessons learned and improvements made from them. The fact that mistakes were made in early designs is known, but hind sight being 20/20 doesn’t invalidate what I said. The USN made improvements in design and materials used in newer vessel construction and probably still is making changes due to further lessons learned. The initial goal in submarine design was to be robust and reliable but, as with every endeavor, mistakes were made. The key is to learn from the, and evidence is that the USN did.

Jim Fox

Rubbish. Bloviate if you must but also re-read what you claimed; implying American design is perfect.
Thresher (SSN-593), the first submarine in its class, sank April 10, 1963 during deep-diving trials after flooding, loss of propulsion, and an attempt to blow the emergency ballast tanks failed, causing it to exceed crush depth. All 129 men on board died. Location: 350 km (190 nmi) east of Cape Cod.
Scorpion (SSN-589), a Skipjack-class submarine, sank May 22, 1968, evidently due to implosion upon reaching its crush depth. What caused the Scorpion to descend to its crush depth is not known. All 99 men on board died. Location: 740 kilometres (400 nmi) southwest of the Azores.

Thresher sank as a result of failure of a gauge pressure line behind the reactor control panel, release of atomised water shorting out and activating a reactor scram. At that time nukes did not carry enough compressed air to blow tanks and having lost power she could not surface using hydroplanes.

greybirdtoo

I neither implied nor stated that American design is perfect. No design is perfect. In my personal experience, however, they attempted to learn from mistakes and improve designs and operation. What I said was clearly that and not, as you stretched to say, perfect design.

As for your analysis of the Thresher failure, it’s all supposition and you state it as if it’s fact. There are several theories as to what _exactly_ happened and the only sure thing is that the emergency blow failed due to moisture in the HP air causing freezing and thus clogging the blow lines, and not inadequate supply of air as you stated. Also, the communications from the Thresher were of a “minor difficulty,” and a piping failure at test depth as you describe would definitely _not_ be classified as such. Also, you pretend to know exactly where the supposed piping failure occurred with no such knowledge possible since such was not communicated during the incident. What you state is one _theory_ that some evidence I’m aware of doesn’t support. So if there is bloviation look in the mirror.

Both of the failures happened in the early days of US nuclear sub design, and the _fact_ that there haven’t been any more supports my statement that they made improvements to design and materials (which was taught in NNPS) based, in part, on what was known and suspected of those disasters. As I previously stated, the _goal_ was to be robust and reliable. That statement in no way can be reasonably construed to mean the designs were perfect. When there were failures, small or catastrophic, they were examined and improvements were made in each new design. So how about reading what I write, and not stretching to interpret it to mean what you want so you can attack it.

Jim Fox

OK, whatever. The MOD(N) team were told categorically that the failure [that was the most likely cause of the scram] that was definitely the ultimate cause by none other than the SENIOR U.S. INVESTIGATOR WHO WAS TEAM LEADER IN UK.

greybirdtoo

What you said previously was “Thresher sank as a result of failure of a gauge pressure line behind the
reactor control panel, release of atomised water shorting out and
activating a reactor scram” as if it was a definite fact. That’s a pretty particular location which was not definitely known, even though you said it was. It was and is a best guess based on information available at the time.

There is contradictory information in that an accompanying sub (Skylark) reportedly didn’t record any flooding sounds in SOSUS data, which was classified at the time of the incident and not released to the board of inquiry (which was nonsense, they should have been cleared and fully briefed.) There was a later report released in 2013 that indicated, based at least in part on SOSUS data that there had been no flooding and the likely root cause was an electrical bus failure.

So, again, your affirmation that you KNOW the cause of the crash is nonsense. The best that can be hoped for without the ability to actually examine the sub is use data from similar subs to make an educated guess.

1. According to official Navy reports, the Thresher’s sinking was quite likely the result of the failure of one or more seawater pipe welds. This likely led to the shorting out of an electrical panel, which shut down the reactor and caused other problems.

2. Because of its speed, the Thresher relied more on its diving planes and deck angle to achieve desired depth, not unlike an airplane. But with the propulsion system compromised and the ship filling with water and sinking, an emergency attempt was no doubt made to blow out the seawater ballast tanks with compressed air.
This was also met with failure. In tests with a sister sub, it was discovered that the rush of compressed air into the ballast tanks resulted in a rapid ice buildup in the air line “strainers,” clogging them.

This last signal received is baffling- by this time it would have been obvious that the reactor had scrammed… “minor difficulty”???

It may be that we were misinformed re the ‘inadequacy’ of compressed air supplies but it is not impossible that at 1000 ft [30+ atmospheres] it would require vast quantities at high pressure to restore positive buoyancy.
Speed of release would have had an effect on the freezing issue…

“The only sure thing” is that freezing occurred in a test on a sister vessel; does not PROVE that’s what happened in Thresher.

I am always open to correction…

greybirdtoo

First, you _did_ “presume to know something” as I quoted in in my post following your previous post, you gave a fairly specific location for the leak. Which is pretty presumptuous to me.

The report you keep referring to as if it was conclusive is based on information released to the investigative team at the time, which later information shows was incomplete as classified information on SOSUS data was, in my opinion, wrongly withheld.

As for the emergency blow attempts, the accompanying sub detected one or more attempts that were unsuccessful due to the ice buildup (which was in the timeline given in the original examination as well as the later one done in 2013 which had access to the SOSUS data). If there were indeed multiple attempts at emergency blow, then the freezing would be the more likely scenario. Since, if there were indeed insufficient air to blow the ballast, multiple attempts couldn’t have been made as the HP air compressors wouldn’t have been able to fill the tanks quickly enough for a second attempt. If that data was incorrect, then there would indeed be a possibility that insufficient air in the tanks was the immediate cause of the failure.

As for the last garbled message, it makes perfect sense if you realize that a reactor scram, which has a known recovery procedure, is relatively minor and recoverable. (I don’t know exactly how much they drilled on the recovery procedure at that time, but it was pretty significant later on, possibly due the 2 sub failures.) A leak at test depth, however small, would _never_ be called a “minor difficulty” in any event. It would have also caused a pretty large noise signature which should have been picked up by SOSUS, but apparently wasn’t (at least as far as released information shows, I wouldn’t be surprised if further information was withheld in the name of security).

All of that being said, I never said that mistakes haven’t been made (and probably new ones are being made right now), just that they attempted to learn from them and correct deficiencies in future designs and operationally by training and changing operational and emergency procedures. Any naval service likely does the same, although I don’t have any direct experience with any other. The people I’ve met who have seem to confirm that, though.

http://peakvt.blogspot.com PeakVT

“The molten salt reactor (MSR), predecessor of the LFTR, lost out to the LWR in the early ’50s for a simple reason. When Navy Admiral Hyman Rickover got wind of the possibilities of nuclear power, he wanted and got nuclear-powered submarines. Unfortunately for the MSR, molten salt would explode violently if it accidentally contacted water.”

This is wrong. First, liquid sodium is not the same as molten salt. Reactors with liquid sodium as a coolant are classified as liquid metal fast reactors (LMFR), and are also often called fast breeder reactors (FBR). Though sodium is a component of many salts, in the case of LMFRs the sodium is pure and is not a salt. Second, MSRs were never seriously considered by the USN. Only PWRs and LMFRs were ever constructed for the USN. The only two MSRs built were the Aircraft Reactor Experiment, built for the Air Force, and the Molten Salt Reactor Experiment, built by ORNL.

jhewitt123

Thanks for pointing out the oversight.

Michael Grimshaw

I have never heard of molten salts reacting violently with water – even in the original MSRE. So I asked the expert: “Is this a misstatement, or did
they use a different salt in the MSRE? I have read several times that
FLiBe salts are non-reactive with water and have a very low water
solubility.”

His response: “This is a misstatement. He is confusing metallic liquid sodium for liquid fluoride salt. Fluoride salts do not react vigorously with water.

http://peakvt.blogspot.com PeakVT

“Our looming medical isotope problem is irresponsible and inexcusable as these isotopes are critical to patient diagnoses and treatment. Any health care system which fails to provide for their reliable procurement will only accelerate current medical cost inflation.”

Leaving aside the validity of these assertions, they do not make a good case for LFTRs. Medical isotopes can be produced with other types of reactors, which are better understood and have been implemented successfully before in this country, and elsewhere. It would be much cheaper and easier to build a small scale HWR (which is what Canada uses to produce isotopes) than to go through the R&D process needed to make LFTRs viable at any size.

jhewitt123

If Kirk Sorensen told me that I might believe him. A lot of things might be much cheaper here. Why then do we, with our tumescent healthcare machine, have virually no capability to make these isotopes other than maybe with a few accelerators, which I am guessing can’t be all that inexpensive?

http://peakvt.blogspot.com PeakVT

“If Kirk Sorensen told me that I might believe him.”

Why? Sorensen has something of a financial interest, in LFTRs, to say the least. Aside from that, Netherlands is replacing its research and isotope reactor for about $650 million. Does Sorenson or any other LFTR advocate think they can develop a production-quality reactor for less?

“A lot of things might be much cheaper here.”

Well, maybe so, in which case that should have been mentioned in the first place.

jhewitt123

Because Sorensen is one of the few in the field with the cojones to put his and his young family’s money where his mouth is. I think he is saying if the bozos with the puppet strings can’t figure a way to make these isotopes, I’ll do it for you, whatever way I can. Sure I agree he has financial interest, but if that was his guiding light maybe he would have stayed in the good job he had. I am not claiming to have your hard earned knowledge of the field, my goal is to cooperate, disseminate, and move the field forward with the little knowledge I can gather and good sense.

Michael Grimshaw

A LFTR would be good method for making medical isotopes is because they can be extracted while the reactor is still operating and while making more energy than it uses. In contrast, accelerator-driven reactors use a lot of energy to make a very small amount of material.
Mr. Sorensen does not imagine that every LFTR will be equipped to remove those short-lived materials. One to three reactors would provide as many medical radio-isotopes the U.S. would need. This is simply one more mark in favor of LFTR; not a primary motivation.

greybirdtoo

There is, and has been for decades, another source for medical isotopes. The High Flux Isotope Reactor (HFIR) at ORNL (http://neutrons.ornl.gov/facilities/HFIR/). It has produced, among other things, the raw materials for Theraseed (http://www.theragenics.com/products) which is used to treat prostate cancer. You should do an article on it some time, I think you’d find it fascinating. (As a disclaimer, I used to work there and so am a bit biased towards the facility.)

jhewitt123

I will run that by the editors, thanks. I have heard about those hot seeds, they apparently are quite effective.

TomSparc

You trust someone on nukes who has no nuke qualifications? Why?

Sorensen is a snake oil salesman. He’s selling a dream that doesn’t exist. It’s astonishing that he seems to have fooled so many people.

http://www.facebook.com/kevpatt Kevin H. Patterson

Advocating… yes. Selling… what? Sorensen is currently pursuing a master’s degree in nuclear engineering at the University of Tennessee. What are your qualifications?

And what exactly is Kirk Sorensen gaining by “selling” this dream to “so many people”? I suggest you do some research, as he has. Then perhaps you will feel the need to educate and raise awareness, as he has. I commend him for devoting his time and money to the idea he believes in.

TomSparc

Sorensen is trying to sell his dream of thorium nukes and looking for someone to give him money. He’s the nuke equivalent of the Simpsons’ monorail salesman.

TomSparc…It seems like you are totally against any form of nuclear fission power generation. If Mr. Sorensen is not independently wealthy, how can he fund his vision of low carbon, safe, cheap energy if he does not ‘sell’ his vision. What Mr. Sorensen is doing is classic entrepreneurship–he has an idea that he thinks will work and he’s putting that idea in the marketplace to look for funding.

I also recommend that you do your research. Mr. Sorensen is not trying to fool anyone. He is the person who retrieved most of the reports from Oak Ridge National Labs and put them on his blog site Energy From Thorium. You can go there are read in great technical detail exactly what the US did from the 1950’s through the 1970’s on MSR technology. Oak Ridge demonstrated many of the features and benefits of this reactor technology. All of the basic physics have been proven. What’s missing is the engineering to work up a design that will be easy to maintain and build. This is why Mr. Sorensen is as energetic and enthusiastic as he is because he knows that the work needed to get a production class reactor is not technically challenging–it just needs the funding to get done.

http://peakvt.blogspot.com PeakVT

“With the world’s most abundant
thorium deposits, [India] initiated a long-term plan to integrate
thorium fuel reactors into its comprehensive nuclear strategy, and now
hopes to have its first successes within a few years.”

You left out an important part of the story here, which is that India plans to use thorium in modified PHWRs, not develop LFTRs (at least in the near future). PHWRs don’t have the same advantages as LFTRs.

jhewitt123

Thanks for posting that incite. India’s tripartite thoro-uranium program seems to have been in place for a while, and consists of several interacting but slow moving parts. If you can sort that out further your comments would be welcome.

http://peakvt.blogspot.com PeakVT

“Richard Martin, a writer for Wired and author of Superfuel: Thorium, the Green Energy Source for the Future, summarized the argument a little more succinctly: the US abandoned thorium reactors because they didn’t produce plutonium bombs.”

I don’t know why anyone thinks this. Almost all US plutonium came out of either dedicated LWGRs at Hanford or dedicated HWRs at Savannah River. The first reactors of those two types went critical well before the first PWR and BWR (and MSR, for that matter) went critical. LWRs produce plutonium, but under typical operating conditions the plutonium has too much Pu-240 relative to the Pu-239, which makes the Pu unsuitable for weapons use.

The decision to stop development of MSRs may have been foolish, but it didn’t happen because LWRs make plutonium.

energy_guy

The production of Purex in those specialized reactors at Hanford and Savannah is largely unknown to the general public and perhaps many supporters of nuclear power in general. People know that plutonium is made in many commercial reactors but not how or why or have any understanding of isotopes, half lives etc so simply mix the weapons and commercial programs together. The early commercial reactors got their early start from weapons people transferring their knowledge in atoms for peace, that also joins the two sides together even if the technologies are quite different.

Now we see some attacks on the LFTR programs because it breeds U-233 and therefore must be useful to bombs not understanding the issue of U-232 contamination. If you really wanted pure weapons grade U-233 you would need a special reactor, it would be called Hanford, same confusion all over.

Great logic there. Hope it takes you far in life.
Every great technology we enjoy today was once the “fantasy” of “techno dreamers”. Difference being, they chased their dream and made it real.
Molten Salt Reactor technology for Thorium fuel cycle was developed and tested at Oak Ridge in the 1960s. We KNOW it will work. It just a matter of getting serious about it. Or we can just dismiss it as “fantasy”.

TomSparc

“Thorium has been considered as a nuclear fuel since the very beginning of the atomic energy era. However, its use in early reactors, whether light-water cooled or gas cooled, has not led any commercial nuclear reactors to operate on a thorium cycle. … Irradiating thorium produces weapons-useable material. … the technology of thorium fuel does not offer sufficient incentives from a cost or waste point of view to easily penetrate the market.” http://web.mit.edu/mitei/research/studies/nuclear-fuel-cycle.shtml

While you keep dreaming, renewables are growing exponentially while falling in cost. You don’t have to be a genius to see where the energy future is heading.

joe johnson

Sorry not that it is unburdened by elections, it is unburdened by people trying to save their business. LWR are junk and dangerous. Thorium seems to be a tech that will work. China and India will be the leaders and we will be second best. Cheap Power is real Power, and whoever owns it will be the winner

kaz

the critical mass of U-233 is smaller than the mass of U-235. this means that they would go through more of it to create the same amount of power. If the equation “unstable+unstable = really unstable. then it would be safer to use U-235. We can also create plutonium with the same method used to enrich the thorium. soooooooo im going to side with uranium on this one

Marcelo Pacheco

Critical Mass is a nuclear weapon concept.
U233 is much better than Plutonium in the thermal spectrum. Thermal spectrum is used only for nuclear power generation. Fast spectrum = more complex and less safe nuclear power.
From now on, I’m talking thermal spectrum:
Th232 gets a neutron -> Th233 -> Pa233 -> U233
U233 gets a neutron -> 85% chance of fission plus 2.3 neutrons in average
If U233 doesn’t fission we get U234 which plus another neutron give us U235 (still a much better fuel than Plutonium)
In the end the odds of a Thorium atom becoming Pu-240 (the first very undesirable transuranic) is less than 0.1% (99.9% of fission)
The odds of a U235 atom becoming Pu-240 is 0.3%
The odds of a U238 atom becoming Pu-240 is 33%
That’s the biggest reason Thorium is so great. Pu-240 and its neutron capture products eventually fission (with a lot of neutrons and patience) but we’d much rather use those neutrons to make more U233 instead of wasting them working through that Pu240/241/242/Americium/Curium. DMSRs can do the latter, LFTR essentially avoids it completely, but at great complexity and still to be done chemical engineering challenges. Still DMSR should be the first step, unless you have a billionaire sugar daddy or the USA govt giving you a lot of money to make it happen.

Jesse Stanley

A major problem for the LFTR in the beginning was it is super hot and begs the need of equipment that can withstand that heat and corrosion. Newer and better alloys are available now than were in the 1960’s. Also, India is not trying to develop a LFTR. Their plan is to use thorium in a breeder because it is a cheaper fuel.

Marcelo Pacheco

The simple, yet complete explanation of why thorium/molten salt reactors never got a serious chance were:
1 – Only the first type of nuclear reactor got a serious chance back then (water cooled ones)
2 – Politics, Politics, Politics
3 – U233 (bred from Thorium) isn’t a good nuclear bomb material, an U233 bomb was tested, but it seriously under performed, there are no known operational nuclear devices in the whole world arsenal with U233 on them
4 – It would have costed several billion dollars in today’s money to get Thorium reactors, the private sector didn’t want to spend big money on any new type of nuclear reactor, and the US govt wanted plutonium breeder reactors (to make bombs)

Molten Salt Reactors and Thorium aren’t locked to each other
1 – There have been water cooled reactors powered by thorium (shipping port reactor last fuel load), there’s such an experiment going on right now (Thor Energy 10%Plutonium-90%Thorium fuel on the Halden Experimental reactor in Sweden)
2 – We could have an MSR running on Uranium or Plutonium fuel, Oak Ridge looked into it in the 80s, there is at least one serious R&D effort to make such a reactor (called the DMSR)
Option number one allows us to capitalize on existing water cooled reactors using a cheaper/more plentiful fuel, burn plutonium stockpiles with safety advantages (plus create a mine of U233 from Thorium spent nuclear fuel for future pure Throruim reactors)

Option number two avoids the extra complexities of the LFTR proposal. I would love to get the full blown LFTR, but specially in today’s US NRC world, the LFTR would be a nightmare to get certified. First get to the market with an economical, much better MSR / Uranium reactor, then incorporate the LFTR advantages once you have the budget to pay for the more advanced features.
I suggest looking into the IMSR from Terrestrial Energy, that Uranium MSR project underway from Canada.

The real reason Thorium is getting such a big push is the rare earth problem. It is a very serious problem, but the rare earth industry isn’t going to fund LFTR development. I wish they did.

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